This disclosure relates to a method for manufacturing a phase-change memory.
A phase-change layer reversibly changes between an amorphous state and a crystalline state. The resistance is higher in the amorphous state than in the crystalline state. A phase-change memory outputs electrical signals corresponding to the resistance of the phase-change layer so that information associated with each state can be read from the phase-change memory. Further, the phase-change memory receives electrical signals for changing the state of the phase-change layer so that information associated with each state can be written to the phase-change memory. Japanese Laid-Open Patent Publication Nos. 2008-182230 and 2008-172221 each describe the structure of the phase-change memory.
When manufacturing a phase-change memory, a recess that is formed in an insulation layer is filled with a phase-change layer. The filling properties of a phase-change material are more superior in an amorphous state than in a crystalline state. Thus, the phase-change layer is usually in an amorphous state when the recess of the insulation layer is filled with the phase-change layer. Then, the phase-change layer in the recess is annealed and shifted to the crystalline state. However, the film density is lower in the amorphous state than in the crystalline state. Thus, the phase-change layer contracts as the phase-change layer shifts to the crystalline state. This may form a void in the recess of the insulation layer.